List the three nutrient cycles present in an ecosystem.
Nutrient cycles are also called as biogeochemical cycles as they help convert the elemental form of essential minerals into biochemical form for utilization by living organisms. The three important nutrient cycles of the ecosystem are the carbon cycle, the nitrogen cycle and the phosphorous cycle.
Nitrogen has a vast atmospheric abundance but is not present in a useable form for many organisms. Nitrogen fixers convert nitrogen into ammonium and nitrates to be taken up by plants and passed onto animals.
Phosphorous is the integral part of the building blocks of nucleic acids, ATP and lipids that make up the very living system on Earth. Though ubiquitous in living organisms, abundance of phosphorous in nature is very low.
Carbon forms organic molecules such as carbon dioxide and carbohydrates. Carbon is exchanged between organisms and the atmosphere through respiration, photosynthesis, burning of fossil fuels, sedimentary deposits of calcareous rocks and decomposition.
As a follow up, provide a brief outline of the carbon cycle.
Carbon enters the ecosystem through photosynthesis where plants utilize atmospheric CO2 and sunlight to form carbohydrates and release oxygen (O2). These carbohydrates are consumed by primary consumers which in turn are consumed by secondary and tertiary consumers.
Producers and consumers respire to release CO2 back into the atmosphere. Upon death, the carbohydrates and organic carbon compounds are released into the soil through decomposition. This process, over a long period of time, results in formation of fossils. Fossils are burned for fuel, thus releasing trapped carbon in the form of CO2.
Atmospheric carbon dioxide (CO2) dissolves in water to form carbonates and bicarbonates that are used by aquatic primary producers. Some of the carbonates and bicarbonates maybe precipitated forming calcareous deposits.
List the main concepts of 'landscape ecology' as defined by Wu and Hobbs. What is the modern definition of 'geographic ecology'?
Wu and Hobbs defined landscape ecology in 2002 as ‘the study of the relationship between spatial pattern and ecological processes over a range of scales’. Briefly, landscape ecology is interdisciplinary as it has application in managing natural resources, planning land-usage and conservation of biodiversity; it is the only branch of ecology that takes into account humans and their interaction with the environment such as effect of economic stress due to resource depletion or mining, population genetics, anthropogenic sounds (Wu, 2012); landscape ecology rests on the term spatial heterogeneity (uneven distribution of various ecological, geological, topological and biological units over a vast scale).
The idea of landscape ecology is similar to geographic ecology which was defined by MacArthur (1972) as “search for pattern of plants and animal life that can be put on a map”. Today geographic ecology is defined as “study of ecological structure and process at large geographic scales”. Both the concepts talk about integrating geographic structures with ecological structures.
List and briefly describe the two large scale atmospheric and oceanic phenomena that influence ecological systems globally.
El Nino Southern Oscillation is a large atmospheric and oceanic phenomenon that affects the climates of North America, South America, Southern Asia, Australia, parts of Africa and parts of Europe. El Nino and La Nina are the two opposite phenomena studied under El Nino Southern Oscillation.
During normal conditions high pressure exists in the Eastern Pacific near the Americas and low pressure in the Western Pacific near Indonesia and Australia. This gives rise to the easterly winds that blow from the high pressure area to low pressure area along the equator pushing the warm water away from the Eastern Pacific and pooling it into the Western Pacific. Meanwhile in the Eastern Pacific region upwelling of the cooler water causes the air to cool down and become dry. The air in the Western pacific becomes warm and gathers moisture causing rainfall over Indonesia, Australia, Southern Asia and parts of Africa. This circulation of warm air rising over the Western Pacific and sinking into the cooler Eastern Pacific is called as Walker circulation. These conditions intensify during La Nina when the Eastern Pacific is cooler than average and the Western Pacific is warmer than average causing floods in the Western Pacific regions and drought in the Eastern Pacific regions.
During El Nino, the pressure over the Western Pacific is high and temperature is lower than average while the barometric pressure is low and temperature is high in the Eastern Pacific. The Walker circulations are reversed and the wind blows westward with great force gathering moisture and causing heavy rainfall over the Americas but causing drought in the Western Pacific region.
References:
Molles, M. C., & Cahill, J. F. (2008). Ecology: concepts and applications. 4/e. Dubuque, IA: WCB/McGraw-Hill.
Wu, J., & Hobbs, R. (2002). Key issues and research priorities in landscape ecology: an idiosyncratic synthesis. Landscape ecology, 17(4), 355-365.
Wu, J. (2013). Key concepts and research topics in landscape ecology revisited: 30 years after the Allerton Park workshop. Landscape Ecology, 28(1), 1-11.
